This sounds to be pure... ahem, a rumor and that's it.
Several years ago a rumor was insisting that Nikon would release a
FM3D, that would have been : a FM3A with the 17x24 CCD sensor taken off the D70s, but with semi-auto and manual metering modes only, no AF, but the ring and dot around its F bayonet for mounting the AI and AI-S lenses on that body and get light metering.
That was pure... ahem, a rumor. We could even see photos of the camera on fantasy blogs like the one which is linked to on this thread.
So, I for sure don't expect that rumor about that "digital SP" to be true. Pure... ahem, rumor.
BTW I don't see the point of having such a "digital rangefinder". Rangefinder cameras are nice in that they don't need batteries, have a full mechanical shutter, an optical focusing system, silent
modus operandi, etc.
As soon as a camera needs a SD card, a battery, a firmware, a LCD screen, an electronic shutter to work, well, I prefer that camera to be a (D)SLR for the comfort of the viewfinder and the AF, plus the matrix and spot metering etc.
What I would want from Nikon is that they do not continue to leave the AI and AI-S lenses owners on the roadside. Being obliged to buy at least a D300 to have metering with my AI-S lenses for which I paid top dollars not a century ago is beyond me.
An updated D40x (which is a entry-level small plastic body yet 10MP sensor rich and has enough features to take good photographs once in the hands of an experienced photographer) with the coupling ring and dot for mounting the AI-S and AI lenses and having at least one metering mode (central weighted is fine) plus AE-lock is hundreds of times more expected by many Nikon nuts than this so-said digital RF mounting lenses that don't exist yet !